8,780 research outputs found

    A vertical monolithic combination of an InGaAsP/InP laser and a heterojunction bipolar transistor

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    A DH InGaAsP/InP mesa laser and a DH InGaAsP/InP mass-transport laser were successfully put together with an InGaAsP/InP heterojunction bipolar transistor in a vertical configuration. A laser threshold current as low as 17 mA and an output laser power of over 30 mW were achieved. Base injection current-controlled optical bistability and optical switching were demonstrated

    Solar modulation of cosmic ray intensity and solar flare events inferred from (14)C contents in dated tree rings

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    The delta 14C values in 42 rings of a white spruce grown in Mackenzie Delta was measured as a continuing effort of tracing the history of solar modulation of cosmic ray intensity. The delta 14C values in six rings were measured, in search of a 14C increase due to two large solar flares that occurred in 1942. The results are presented

    Illusion optics: The optical transformation of an object into another object

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    We propose to use transformation optics to generate a general illusion such that an arbitrary object appears to be like some other object of our choice. This is achieved by using a remote device that transforms the scattered light outside a virtual boundary into that of the object chosen for the illusion, regardless of the profile of the incident wave. This type of illusion device also enables people to see through walls. Our work extends the concept of cloaking as a special form of illusion to the wider realm of illusion optics.Comment: Including a paper and its auxiliary materia

    Fragmentation and OB Star Formation in High-Mass Molecular Hub-Filament System

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    Filamentary structures are ubiquitously seen in the interstellar medium. The concentrated molecular mass in the filaments allows fragmentation to occur in a shorter timescale than the timescale of the global collapse. Such hierarchical fragmentation may further assist the dissipation of excessive angular momentum. It is crucial to resolve the morphology and the internal velocity structures of the molecular filaments observationally. We perform 0".5-2".5 angular resolution interferometric observations toward the nearly face-on OB cluster forming region G33.92+0.11. Observations of various spectral lines as well as the millimeter dust continuum emission, consistently trace several \sim1 pc scale, clumpy molecular arms. Some of the molecular arms geometrically merge to an inner 3.01.4+2.8103^{{\scriptsize{+2.8}}}_{{-\scriptsize{1.4}}}\cdot10^{3}\,MM_{\odot}, 0.6 pc scale central molecular clump, and may directly channel the molecular gas to the warm (\sim50 K) molecular gas immediately surrounding the centrally embedded OB stars. The NH3_{3} spectra suggest a medium turbulence line width of FWHM\lesssim2\,km\,s1^{-1} in the central molecular clump, implying a \gtrsim10 times larger molecular mass than the virial mass. Feedbacks from shocks and the centrally embedded OB stars and localized (proto)stellar clusters, likely play a key role in the heating of molecular gas and could lead to the observed chemical stratification. Although (proto)stellar feedbacks are already present, G33.92+0.11 chemically appears to be at an early evolutionary stage given by the low abundance limit of SO2_{2} observed in this region.Comment: 37 pages, 23 figure

    Effects of ZbZ_b states and bottom meson loops on Υ(4S)Υ(1S,2S)π+π\Upsilon(4S) \to \Upsilon(1S,2S) \pi^+\pi^- transitions

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    We study the dipion transitions Υ(4S)Υ(nS)π+π\Upsilon(4S) \rightarrow \Upsilon(nS) \pi^+\pi^- (n=1,2)(n=1,2). In particular, we consider the effects of the two intermediate bottomoniumlike exotic states Zb(10610)Z_b(10610) and Zb(10650)Z_b(10650) as well as bottom meson loops. The strong pion-pion final-state interactions, especially including channel coupling to KKˉK\bar{K} in the SS-wave, are taken into account model-independently by using dispersion theory. Based on a nonrelativistic effective field theory we find that the contribution from the bottom meson loops is comparable to those from the chiral contact terms and the ZbZ_b-exchange terms. For the Υ(4S)Υ(2S)π+π\Upsilon(4S) \rightarrow \Upsilon(2S) \pi^+\pi^- decay, the result shows that including the effects of the ZbZ_b-exchange and the bottom meson loops can naturally reproduce the two-hump behavior of the ππ\pi\pi mass spectra. Future angular distribution data are decisive for the identification of different production mechanisms. For the Υ(4S)Υ(1S)π+π\Upsilon(4S) \rightarrow \Upsilon(1S) \pi^+\pi^- decay, we show that there is a narrow dip around 1 GeV in the ππ\pi\pi invariant mass distribution, caused by the final-state interactions. The distribution is clearly different from that in similar transitions from lower Υ\Upsilon states, and needs to be verified by future data with high statistics. Also we predict the decay width and the dikaon mass distribution of the Υ(4S)Υ(1S)K+K\Upsilon(4S) \rightarrow \Upsilon(1S) K^+ K^- process.Comment: 25 pages, 8 figures, predictions of the decay width and the dikaon mass distribution of the Υ(4S)Υ(1S)K+K\Upsilon(4S) \rightarrow \Upsilon(1S) K^+ K^- process added, more discussions adde

    Biomimetic coating of apatite/collagen composite on poly L-lactic acid facilitates cell seeding

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    Collagen and apatite were co-precipitated as a composite coating on poly L-lactic acid (PLLA) in an accelerated biomimetic process. The coating formed on PLLA films after 24 hours incubation was characterized. Saos-2 osteoblast-like cells were used to evaluate the cell seeding on this biomimetic composite coating. It was shown that cell seeding on PLLA films with the composite coating was greatly improved. PLLA coated with submicron collagen fibrils and submicron apatite paticulates can facilitate bone tissue engineering. ©2005 IEEE.published_or_final_versio

    Strong decays of Tcsˉ0(2900)++/0T_{c\bar s0}(2900)^{++/0} as a fully open-flavor tetraquark state

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    We have studied the strong decay properties of the recently observed Tcsˉ0a(2900)++/0T^a_{c\bar s0}(2900)^{++/0} by considering it as a cudˉsˉ/cduˉsˉcu\bar{d}\bar{s}/cd\bar{u}\bar{s} fully open-flavor tetraquark state with I(JP)=1(0+)I(J^P)=1(0^+). In the framework of QCD sum rules, we have calculated the three-point correlation functions of the two-body strong decay processes Tcsˉ0a(2900)++Ds+π+T^a_{c\bar s0}(2900)^{++}\rightarrow D_s^+\pi^+, D+K+,Ds+ρ+D^+K^+, D_s^{\ast +}\rho^+ and Ds1+π+D_{s1}^+\pi^+. The full width of Tcsˉ0a(2900)++/0T^a_{c\bar s0}(2900)^{++/0} is obtained as 161.7±94.8161.7\pm94.8 MeV, which is consistent with the experimental observation. We predict the relative branching ratios as Γ(TDsπ):Γ(TDK):Γ(TDsρ):Γ(TDs1π)1.00:1.10:0.04:0.43\Gamma (T\rightarrow D_s\pi):\Gamma(T\rightarrow DK):\Gamma (T\rightarrow D_s^{\ast} \rho):\Gamma (T\rightarrow D_{s1}\pi)\approx1.00:1.10:0.04:0.43, implying that the main decay modes of Tcsˉ0a(2900)++/0T^a_{c\bar s0}(2900)^{++/0} state are DsπD_s\pi and DKDK channels in our calculations. However, the PP-wave decay mode Ds1πD_{s1}\pi is also comparable and important by including the uncertainties. To further identify the nature of Tcsˉ0a(2900)++/0T^a_{c\bar s0}(2900)^{++/0}, we suggest confirming them in the DKDK and DsπD_{s}\pi final states, and measuring the above ratios in future experiments.Comment: 9 pages, 7 figure
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